Field of the Invention
The present invention relates to a method of producing a membrane electrode assembly. The membrane electrode assembly includes a solid polymer electrolyte membrane and electrodes provided on both sides of the solid polymer electrolyte membrane, respectively. Each of the electrodes includes a gas diffusion layer and an electrode catalyst layer.
Description of the Related Art
A unit cell of a solid polymer fuel cell is formed by sandwiching a membrane electrode assembly between a pair of separators. The membrane electrode assembly includes a pair of electrodes (an anode and a cathode) and a solid polymer electrolyte membrane interposed between the electrodes. The solid polymer electrolyte membrane is a polymer ion exchange membrane.
Each of the pair of electrodes includes an electrode catalyst layer and a gas diffusion layer. The electrode catalyst layer faces the solid polymer electrolyte membrane, and serves as a reaction field of electrode reaction. The gas diffusion layer is made up of porous carbon paper etc. where the reactant gas is diffused through the gas diffusion layer to supply the reactant gas to the electrode catalyst layer.
For example, a production method described in Japanese Laid-Open Paten Publication No. 2009-283241 is known as a method of producing a membrane electrode assembly of this type. In this production method, a solid polymer electrolyte membrane and gas diffusion layers are stacked together in a stacking direction in a manner that electrode catalyst layers are interposed between the solid polymer electrolyte membrane and the gas diffusion layers, and the resulting stack body is pressed by the heated mold from both sides in the stacking direction to perform hot pressing. The heat of the mold is transmitted to the electrode catalyst layers and the solid polymer electrolyte membrane through the gas diffusion layers. In this manner, the gas diffusion layers, the electrode catalyst layers, and the solid polymer electrolyte membrane are joined integrally by thermo-coupling to obtain the membrane electrode assembly.